all for the challenge
by Xephonia
Summary: Ryouga wants to learn how to kiss well so he can beat Kaito at it. He asks Rio for advice. Her teaching strategy is quite effective. [First time sex] [AU where incest is not illegal and not even half as stigmatized as it is in our world. It's just very unusual.] [TW: Incest]


Kamishiro Ryouga's life is nothing but a series of questionable life choices.

You see, he's been going to a bar with Rio every Friday night, because letting his sister go to a bar alone seemed a bad idea to him and he had too much alcohol and—

Now he's in some sort of... thing.

It's not a relationship, it's not even romantic, it's not... anything, really. The guy is called Kaito.

He pisses Ryouga off, Ryouga pisses him off, but they kind of find each other hot, so quite often they are kissing, sometimes they just have dumb drinking competitions and sometimes— rarely— they talk about life and why it sucks.

None of that would be an actual problem if they didn't make a goddamn challenge out of everything.

Basically they've been telling each other how shitty the other is at kissing— it's too much teeth to even be called kissing sometimes— and Ryouga intends to be less shitty than Kaito.

So on a Saturday night, he asks the only available person for advice—

"Rio." They're on the couch, Rio is busy with her phone and Ryouga has stared at the ceiling for too long.

"Hm?" Rio looks up from her phone.

"How do people... kiss good?"

Rio puts her phone away and smiles when she sees Ryouga's flushed face. "Oh~ Is it because of Kaito?"

"It's not, I just wanna—"

"Prove that annoying guy you're better at it?"

"Yeah. How do you know?"

"Just a feeling."

Ryouga doesn't quite buy it, but he knows Rio wouldn't tell him how she knows anyway. "So, any advice?"

"Stop trying to eat his face."

"Wha—"

Rio gets up and walks over to Ryouga, grabs him by the collar and kisses him.

He takes a moment to register what the heck is going on, then he goes along with it.

It's. Teethy. Like with Kaito, but different.

Ryouga breaks the kiss after a bit. "What was that about?"

"This is stuff that words don't explain quite well. This was an example of how you do it by the way." Rio sighs. "Also, you taste like beer."

Ryouga points at the almost full bottle on the table because, duh. "At least warn me next time."

"You can just be prepared next time." Rio sits down on Ryouga's lap like that's the most normal thing to do on a Saturday night in one's living room.

And actually, for them, it kind of is.

Ryouga remembers the times he's carried her bridal style, the times he's seen her naked, and he figures they never really had all that many privacy barriers to begin with.

"So, are we really making out right now because you're too lazy to come up with a proper explanation?"

"Yeah."

"You realize that's damn narcissistic, right? Given that we're twins and all."

"That's precisely why it's fine, isn't it?" Rio smiles.

Ryouga sighs. "Fine."

Right after, Rio's lips are on his again, and Ryouga feels like it really is narcissistic, but oddly fine. This time, it's not teeth, either (at least not on Rio's part), and it's mostly lips; to be exact, Rio sucking on his lower lip and—

Ryouga feels his cheeks heat up because it's good.

Rio breaks the kiss, taking him back to the reality of the situation. Ryouga is aware of his hands on her back and her hands in his hair, and he wonders when they got there.

"Alright. So. The basic problem is that you keep trying to French kiss Kaito, but you guys have no buildup or proper body language, so it all goes wrong."

"And what about what you did was different?"

"I didn't smash my open mouth on your open mouth."

"Oh."

"You're really bad at this, you know."

Ryouga strokes her back a little. "That's why you're teaching me, aren't you?" He smirks.

"Are you trying to flirt with me?" Rio raises an eyebrow.

Silence.

Then, reluctantly,

"Maybe?"

Rio sighs. "You should really get some control over your hormones."

"You're the one who used my request as an excuse to make out with me." Ryouga scowls.

"You don't seem to have a problem with that; at least your crotch definitely doesn't."

Ryouga can't deny it, and he leans in for a kiss, mimicking Rio's movements from earlier as good as he can, and the way her grip on his hair tightens tells him that he's doing well.

He softly nibbles on her lower lip now, trying to keep in mind to not overuse his teeth—

(He realizes he really just has a thing for it.)

—and she responds by doing the same on his upper lip.

(He's very aware of their position right now, and he tries to not show it.)

From the way Rio's left hand traces over his hip, Ryouga figures she knows what he's thinking anyway.

Suddenly, he feels her tongue against his lips, and he opens them without thinking much, responds with his own tongue fast, trying to not have their 'battle' in his mouth, but in hers.

Turns out to be harder than expected, because Rio is persistent and this is just like one of their squabbles, but worse.

Ryouga is about to 'win' their 'fight' when Rio shifts a little on him— Ryouga is sure the way she grinds against his crotch as she does is 100% on purpose— and he is too distracted (in a quite positive way), leaving her the opportunity to push his tongue back into his mouth.

For a lack of breath, they break apart; their breathing is heavy and Ryouga can tell it's for more than one reason.

"So, do you get how it works now?" Rio asks with a smile. It's one of her victorious smiles that Ryouga can't stand.

Ryouga scowls. "You didn't play fair."

"You just don't know everything that's allowed yet. Well, you'll have no problems with Kaito now, that's for sure." She licks over her lips, and Ryouga's eyes are almost glued to the movement. "Well, we're done here, aren't we?"

"Oi, this is a really bad moment to stop."

(Mistake.)

"Well, Ryouga, what should I do about that?" Rio lazily traces over his chest, and she seems to take some sort of satisfaction in his anticipation.

"How about not teasing me," Ryouga hisses and kisses her neck softly, sucking on one spot slightly; and then—

"Ah~", the sound escapes Rio's lips.

Ryouga stops and smirks. "Oh?"

Rio's face is flushed and her eyes flutter open. "What was that for?"

"Revenge, obviously."

Their lips meet again; this time, Rio is a lot faster about getting their tongues involved; and Ryouga can tell that they'll both gain something out of it.

Rio's hand slides under Ryouga's shirt— he doesn't mind, his clothes were starting to feel unnecessary at this point anyway— and lifts it over his head, and he mimics the motion on Rio right after.

Rio has always had quite the simple taste in underwear, and Ryouga appreciates it— too much oddities and spending unnecessary time to get the clothes off someone's body is just not his thing.

At that moment, the thought that he originally just wanted to know how to beat Kaito at kissing and now he's having sex with Rio crosses his mind, but he shoves it away in favour of kissing down her neck while taking off her bra.

Ryouga is about to wonder where to go from there when he feels Rio's hand between his legs, gently rubbing his member through his clothes.

"Do you even," Ryouga struggles to have a steady breath. "Know how to do any of this?"

Rio smirks. "You seem to enjoy it, so it appears that I know enough." This time, it's her who kisses his neck, and he squirms a little, surprised by the pleasure that comes from it.

"Should've known that you're just as sensitive as I am there," Rio says, and her breath against his neck makes Ryouga shiver.

Ryouga tries to get out a coherent answer, but Rio licks over his neck and all he gets out is a gasp.

(Totally not a moan. Totally.)

As Rio gets out of her pants and panties, Ryouga tries to clear his head enough to get one question out before it's too late.

"Wait, Rio, isn't this—"

"My first, your first? Yeah."

Ryouga guesses she appears to have no problems at all with it. He doesn't, either; he gets it.

Before he can open his mouth, Rio continues, "And I'm on the pill anyway, so don't worry."

Ryouga knows that's true because he's seen her take it often enough, so he figures it really is fine. Moments later, Rio pulls down his pants and boxers, and he's painfully aware of how hard he is and how victorious Rio must feel.

With a lot less expertise than she usually has, Rio slides her hand over Ryouga's member, stroking it.

(Ryouga notices how swollen her lips are, probably from the kissing, and wonders whether her actions or her lips turn him on more right at that moment.)

He tries to not make noises as Rio touches his dick, but it's hard (pun intended) and he makes them anyway.

Rio smiles. "You're really easy to please, you know that?"

"Shut up," Ryouga mutters, but it lacks its bite and gets lost in a moan when Rio puts her lips on his erection.

Slowly— slow enough for Ryouga to consider asking her to go faster, not slow enough to not feel incredibly good— Rio runs her tongue over it, and Ryouga notices that she's fingering herself as she does.

(Through his half-opened eyelids, he tries to make out what spots she touches to feel good.)

"Faster," he demands, but Rio removes her tongue.

"It'd be boring if you came like that, wouldn't it? Let's switch."

The switch is done quite quickly, and while Ryouga does want to get off, he also wants both of them to get something out of it, so he softly rubs Rio's clitoris, and smirks when he sees her squirm. "It really is that sensitive, huh."

This time, he licks it, and it's satisfying to hear and feel Rio's reactions; her moans and how she isn't like her usual rude self at all right now.

When she buries her hands in his hair to pull him closer, he lets it happen; he wanted to, too, earlier, but he'd hesitated.

(Ryouga realizes he kind of likes having his hair pulled, and he wonders if it's the same for Rio.)

He alternates between kissing and licking her clitoris while stroking himself and her thighs, and he realizes it really, really is good.

Rio's squirming intensifies, and he realizes he can't let her cum just yet, so he gets up again and leans over her. "What position?"

"That question is so unsexy, Ryouga."

"Try to do it better."

"Just do me right here."

That was pretty straightforward, Ryouga thinks, and he carefully slides two fingers inside, waiting for Rio to nod before he starts scissoring her.

He takes his time exploring the unknown grounds, and suddenly he feels Rio's hand on his erection again.

"Just... do it already," she demands, and after Ryouga puts in a third finger for a bit to check if Rio is really alright, they switch positions slightly so Ryouga can align himself in front of her entrance.

"Tell me if it hurts," he says before slowly inserting his dick, and he feels Rio's muscles tighten around him a bit before loosing up again, and he pushes his whole length in, eliciting a moan from Rio.

"Don't wait too much," she demands with a breathy voice. "It's not fun that way."

Ryouga decides to take her by her word, and he leans over her and starts thrusting. He realizes quickly that she's moving her hips to match his pace.

It's hot.

His lips meet her collarbone, and he's sure the way he sucks will leave a mark, but he's too turned on to care.

His thoughts are melting into the arousal, and he can tell it's the same for her because her hands are in his hair again and it hurts but it feels good and—

"How," Rio begins and bites her lip to silence her moan. "Close are you?"

"Pretty close," Ryouga says, and it's a bad way of measurement, but better than none. "How about you?" As he says that, he thrusts a little slower, moving one hand to her clitoris again as he keeps thrusting, the movement making his hand rub the spot with every thrust.

It takes Rio a few moans— or screams, their sounds have started to be both at this point— to reply. "Me, too."

Ryouga accelerates his movement now, rubbing her clitoris a little faster, he doesn't think anymore and just keeps going—

Rio is biting her lip when she cums, but the sound is still there and her muscles contract around Ryouga's dick, making him come, too.

(And he thinks he's shouting her name, but he can't quite tell through the orgasmic haze.)

Ryouga thrusts a slow few more times to calm down before slowly pulling out, trying to catch his breath.

Rio just lies there for a few more seconds before slowly getting into a sitting position again.

"Was it," they begin simultaneously and stop in their sentence.

"Good?" Ryouga finishes the sentence.

Rio nods. "From your sounds, I can tell it was the same for you."

"...Tch. You really shouldn't have bitten your lip when you came."

"That'd give you too much satisfaction." Rio smirks. "Anyway, let's get cleaned up."

* * *

Later that night, right before going to bed, Ryouga remembers something important.

"Wait, how did you know about what I wanted advice for earlier?"

"I told you, I just knew." Rio looks at the red mark on her collarbone and scowls. "You really had to do that, didn't you?"

Ryouga smirks for a bit when he sees the mark, but then he gets serious again. "There's no way you knew. I mean, I have more than enough advice for next Friday now, but still."

"Because Kaito asked me the same thing."

"Wait, is that how you knew what the problem was?"

"Yeah. I helped him out a little."

"Does that mean, you two had...?" Ryouga's face is tinged red a little.

Rio smirks now. "Would you like that?"

"...Maybe?"

"Buuut we didn't have sex.. I told you, you're my first. I did teach Kaito how to kiss the way I taught you, though," Rio stretches herself and gets to putting on her pajamas. "I'd not mind joining you two, though, and I doubt any of you minds, either."

"I definitely don't mind."


End file.
